Phase-splitting system



Dec. 15, 1925- 1,565,434

c. LE 6; FORTESCUE PHASE SPLITTING SYSTEM Filed March 5, 1921.

Phzwe A- Phzue B.

5 1T I I I? 2/ W 2 Phase/1. 22

Plume/4.

Phase B.

' INVENTOR 6x3 40 harlesLe/"orfescve BY ATTORNEY Patented Dec. 15, 1925.

UNITED STATES PATENT OFFICE.

CHARLES IIE G. FORTESCUE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

PHASE-SPLITTING SYSTEM.

Application filed March 5, 1921. Serial No. 449,725.

To all whom it may concern:

Be it known that I, CHAR ES LE G. FORTESCUE', a subject of the King of Great Britain, and a residentof Pittsburgh, in the county of Allegheny and State of Penn sylvania, have invented a new and useful Improvement in Phase-Splitting Systems, of which the following is a specification.

My invention relates to alternating: current distributing systems and it has special relation to phase-splitting or mod1- fying means whereby polyphase apparatus,

such as motors and the like, may be operated from single-phase supply circuits.

In the prlor art, as represented, for example, by my Patent No. 1,284,292, granted November 12, 1918, various phase-splitting devices of the static type embodying combinations of inductances and capacitances have been devised, but, in all cases, the necessary inductance values have been provided for the most part, by choke coils, or the like, that have been separate and distinct from other portions ofthe system, such as the main su ply transformers.

One ect of my invention, therefore, is to provide a phase-splitting system of the character set forth wherein the necessary inductance values are provided by or incorporated in novel main-transformer structures, whereby a double function is served by a portion of the apparatus and the expense of the system is materially decreased.

Viewed from another angle, the object of my invention is to provi e, in a phasesplitting bridge, or the equivalent, a plu rality of inductive reactors that are influen'ced through the agency of inductive action in, or in connection with, the main su ly transformer.

y invention may best be understood by reference to the accompanying drawings, wherein- Figures 1, 2 and 3 are diagrammatic views ofdvarious forms of my present invention; an

Fig. 4 is a semi-diagrammatic view, of a transformer structure which .may be emloyed to advantage in connection with my invention.

Referring to Fig. 1, the s stem here shown comprises a main or supp y transformer 1, which embodies a primary coil. or winding 2 that may be energized fromany suitable single-phase circuit, and. a mam secondary winding or coil 3 that is adapted to supply electromotive force of the same phase relation, as that of the single-phase supply circuit to one phase of the deliver circuit designated as phase A. In addition, the transformer 1 embodies auxiliary secondary coils 5 and 7 of similar form,.the winding 5 being loosely coupled with the primary Winding 2, as conventionally indicated by the arrow 6, and the winding 7 being closely coupled with the primary winding 2.

A relatively smallinductive reactor 8, external to the transformer 1, is connected in series relation with the loosely coupled winding 5, While a condenser 9 or other capacitance device is connected in series relation with the closely coupled winding 7. The junction of the reactor8 and the condenser 9 forms one terminal of the second or quadrature phase B of the delivery circuit.

A relatively small inductive reactor 10 and a condenser or the like 11 are connected, external to the transformer 1, in series relation with the loosely coupled winding 5 on the opposite side of the winding from the reactor 8, and the bridge circuit is completed from the condenser 11 to the closely coupled Winding 7. A point intermediate the winding and the condenser 11 forms the other terminal of the quadrature phase B" In this way, by the provision of the coils 5 and 7 in the main transformer, the necessity of relatively large inductive reactors external to the transformer in the bridge circuit is obviated, and, furthermore, the customary adjustable core members for such external reactors are no longer required, since the desired adjustments may readily be made by providing a plurality of taps on either or both of the windings 5 and 7, as indicated by the arrows. Thus, a relatively simple and inexpensive phase-splitting system of the static type is provided.

Referring to Fig. 2, the supply conductors for phase A, corresponding to the singlephase line voltage, are respectively connected to coils 16 and 19, which are cumulatively wound upon one leg of the main transformer core 18, the oppositeor outer terminal of each of the windings 16 and 19 being connected to the respective conductors for the quadrature phase B.

A plurality of coils 17 and 20 are oppositely wound around the same leg of the core 18 for providing the desired inductive effect in the phase-splitting bridge. The coil 17 is connected in circuit with the primary coil 16 across the phase B and is adapted to act cumulatively with respect .to the coil 16. On the other hand, the coil 20, although connected in circuit with. the coil 19 across phase B, is adapted to act differentially with respect to the other three coils, as indicated by the corresponding arrows.

A second leg of the transformer is rovided with a winding or coil 21, across w ich a condenser 22 forming the condensive part of the bridge is connected. In this way, the main transformer is employed to ste -up the voltage-to the condensive portion 0 the bridge, and any desired variation in the value of this portion to maintain balanced polyphase operation in the phases A and B may be obtained by changing the transformerwinding taps of either the secondary winding 21 or of the primary coils 16 and 19, as indicated by the various corresponding arrows. The coils 17 "and 20, constituting the reactive parts of the phase-splitting bridge, are wound on the same ma netic circuit as the other coils but are di erentially connected so that they have no mutual inductance with respect to the condenser circuitembodying the .coil 21.

In Fig. 3, a main supply transformer 25 is shown as embodying a primary winding 26 and a plurality of parallel-connected secondary windings 27 and 28. An auxiliary transformer 31 is provided. with a primary coil 32 which is connected to the midoints' 27 and 28 of the main transformer 25, whi e p the diagonally opposite point of the bridge is connected by conductors 37 to the opposite terminal of the seconda windings.

Phase A is provide by connectingsuitable conductors across the terminals of the secondary windings 27 and 28 of the main transformer, whereas hase B is obtained by connecting suitab e' conductors to the junction-point of the auxiliary transformer coil 34 and the condenser 36.

By thus tapping the secondary windings of the main transformer at their middle points and inductively connecting such points to the bridge circuits through the agency of the winding 32 and the coils.33 and 34 forming parts of the phase-splitting bridge, the desired reactive effect from the 'viously' described systemsa main transformer is transmitted to the circuits in question.

Desired variations in the value of the reactive portions of the brid may be obtained b changing the num er of turns in the win ings'32, 33 and 34, as indicated by the corresponding arrows.

Fig. 4 shows a transformer structure which may be employed to advantage in connection with certain portions of the prewherein two groups of coils are. so wou'n as to be inopposition, so far as the main flux is concerned.

The illustrated structure comprises a hollow rectangular transformer 40 having an intermediate cross-bar or leg 41, upon which is wounda plurality of oppositel disposed coils 42 and 43. If desired, a s unt magnetic path may be provided comprising magnetizable members or laminated bars 44 and 45 which are located in the center portions of the openings provided by the outer and the intermediate legs of the transformer.

The illustrated structure requires a relatively small amount of space and adds inappreciably to the cost of the main transformer. This structure, in eneral, is known in the art, since similar evices have been employed for sustaining inductance in.

rectifier's, etc.

spond, forexample, to the oppositely-wound coils 19 and 20 in Fig. 2, or to the upper sections of the coils 27 and 28 -or to the two parts of winding 27, for instance, in Fi 3.

It will be seen that I have thus provided a phase-splitting bridge of the static type wherein the necessary inductance values are provided by, or are incorporated in, the main transformer. I

Ido not wish to be restricted to the specific circuit-connections or arrangement of -parts hereinset forth, as various modifications thereof may be made without departing from the spirit and scope of mv invention.

I desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

claim as my invention:

.1. A phase-convertmg system comprising a primary transformer winding, a main secondary winding for producing one phase of the converted system, a plurality of auxiliary secondary windings, and a plurality of ca acitance devices connected in a closed circult alternately with said auxiliary windings to produce a second phase of the converted 1 verted system, said auxiliary windings bewith said primary wlndmg.

ing loosely and closely coupled, respectively,

4. The combination with a single-phase supply circuit, of a transformer associated therewith, phase-splittin means also embodyin portions of sai transformer, and

means lor varying the action of said means by varying the transformer portions embodied therein.

5; An electrical system comprising a rimary transformer winding, a main secon ary winding, a plurality of auxiliary secondary windings, a plurality of capacitance devices connected between the sets of terminals of said auxiliary windings, and means comprising. movable tap-connections on said auxiliary windings for varying the inductance of the circuit thereof.

6. A phase-converting system comprising a primary transformer winding, a main sec- 7 ondary winding for producing one phase of the converted system, a plurality of auxiliar secondary windings, a plurality of capacitance devices connected in a closed circuit alternately with said auxiliary windings to produce a second hase of the converted system, and a plurahty of movable tap-connections associated with-said auxiliary wind- An electrical system comprising a primary transformer winding, a main secondary winding, a plurality of auxiliary sec ondary windings, a plurality of capacitance devices connected between the sets of terminals of said auxiliary windings, said auxiliary windings being loosely and closely coupled, respectively, with said primary winding, and means comprising movable tap-connections on said auxiliary windings for varying the inductance of the circuit thereof.

8. A phase-converting system comprising a primary transformer winding, a main secondary winding for producing one phase of the converted system, a plurality of auxiliary secondary windings, a plurality of capacitance devices connected in a closed circuit alternately with saidauxiliary windings to produce a second phase of the converted system, said auxiliary windings being loosely and closely coupled, respectively, with said primary winding, and a pluralit of movable tap-connections associated wit said auxiliary windings.

In testimony whereof, I have hereunto subscribed my name this 28th day of February, 1921.

. CHARLES LE G. FORTESCUE, 

